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  • ArrayCreate should use the default [[DefineOwnProperty]] internal method instead of Array's

ArrayCreate should use the default [[DefineOwnProperty]] internal method instead of Array's

# Yusuke Suzuki (14 years ago)

Hello everyone,

In 15.4 ArrayCreate algorithm step 7, we use [[DefineOwnProperty]] of A.

Call the [[DefineOwnProperty]] internal method of A with arguments

"length", Property Desciptor {[[Value]]: length, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: false}, and false.

ArrayCreate set A's [[DefineOwnProperty]] to 15.4.5.1 method in step 4, so step 7 calls 15.4.5.1 Array's [[DefineOwnProperty]].

Array's [[DefineOwnProperty]] assumes that 'length' property is always set. Seeing 15.4.5.1 step 1

Let oldLenDesc be the result of calling the [[GetOwnProperty]] internal

method of A passing "length" as the argument. The result will never be undefined or an accessor descriptor because Array objects are created with a length data property that cannot be deleted or reconfigured.

But, in ArrayCreate phase (step 7), A's 'length' property is not set yet. Then assertion in 15.4.5.1 step 1 always fails.

So we should use the default [[DefineOwnProperty]] internal method instead of Array's. I suggest modifying ArrayCreate step 7,

Call the default [[DefineOwnProperty]] internal method (8.12.9) on A with arguments "length", Property Desciptor {[[Value]]: length, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: false}, and false.

, Yusuke Suzuki

# Allen Wirfs-Brock (14 years ago)

this also should be reported to bugs.ecmascript.org

This is a very good catch.

# Yusuke Suzuki (14 years ago)

Thanks for your reply.

I filed this issue to bugs.ecmascript.org, ecmascript#415

, Yusuke Suzuki